C + + Class Design 2 (class with pointer members) __c++

Two class with pointer members (class String)

1. Test code (use effect)

int main ()
{
    string S1 (),
    string s2 ("Hello");          Constructor
    String S3 (S1);               Copy construction
    cout << S3 << Endl;
    s3 = S2;                     Copy Assignment
    cout << S3 << Endl;
}

2 Big Three (three kinds of special functions)

Class String
{public
:
    String (const char* CSTR = 0);
    String (const string& str); parameter is a reference to the same type of object, the copy construct 
    string& operator= (const string& str);//Copy Assignment
    ~string ()/destructor
    char* Get_c _str () const{return
        m_data;
    }
Private:
    char* m_data; 

2.1 ctor & Dtor (structure and destructor)

Inline
string::string (const char* CSTR = 0)
{
    if (CStr) {
        m_data = new Char[strlen (CStr) +1];
        strcpy (M_DATA,CSTR); 
    }
    else{   //Unspecified length 
        m_data = new char[1];
        *m_data = ' n ';
    }
}

Inline
string::~string ()
{
    delete[] m_data;

The 2.2 Class with the pointer members must have copy ctor (copy construction) and copy op (copy assignment)

Deep copy and shallow copy

Deep copy:

Inline
string::string (const string& str) {
    m_data = new Char[strlen (str.m_data) + 1];  Direct access to the private data of another object
                                                //can be interpreted 
    strcpy (m_data, str.m_data);
}

Copy Assignment function:

Train of thought: if the right copy to the left, the step is to clear the left, allocate the same space as the right, complete the copy.

Inline
string& string::operator= (const string& str) {
    if (this = = &str) {  //Detect self assignment, not just efficiency issues return 
        *this;  If not, the behavior may not be defined, see the following figure explained
    }
    delete[] m_data;    Clear left 
    m_data = new char[strlen (str.m_data) + 1];//Open space 
    strcpy (m_data, str.m_data);//Complete copy return 
    *this

Summary: Classes with pointer variables must be copied, copied, assigned, and destructors.